Effect of Acidic Condition on Phenolic Composition and Antioxidant Potential of Aqueous Extracts from Sorghum (Sorghum Bicolor) Bran




The effect of extraction under acidic condition (pH 2) on phenolic compounds and antioxidant potential of aqueous extracts from condensed tannin sorghum bran was investigated. The protective effect of extracts prepared with water (WE) and acidified water (pH 2) (AWE) against free radical-induced red blood cell hemolysis and low-density lipoprotein (LDL) oxidation was determined. The % yield (grams of freeze-dried aqueous extract/100 g of dry sample weight), total phenolic, flavonoid content and 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity were significantly higher in AWE than WE. AWE had 19% higher overall content of identified phenolic acids and flavonoids than WE. AWE showed a significantly higher degree of protection against erythrocyte membrane oxidation than WE. Both extracts showed protective effect against LDL oxidation. However, there were no significant differences in tannin content and oxygen radical absorbance capacity values between the extracts. Extracting sorghum bran under acidic conditions may release bound phenolic compounds thereby improving the health-promoting benefits of extracts from sorghum bran.


The study shows that aqueous extracts with higher phenolic content, antioxidant activity and potential health benefits can be prepared from condensed tannin bran under acidic condition. Using water as a solvent may be preferred over organic solvents because it is cheaper, environmentally friendly and does not require special handling. The aqueous extracts from sorghum bran may be used exogenously as antioxidant functional food ingredients in the formulation of functional foods with potential health-promoting properties. This could improve the economic value of sorghum grain.